U.S. Pat. No. 6,379,327 discloses portable breast pump systems. A portable breast pump system disclosed comprises two breast receptors that are connected to a container by means of a collection tube. A breast pump is connected to the container by means of a vacuum tube. The collection container has a lid through which the collection tube and the vacuum tube are inserted. By operating the breast pump, a vacuum is created in an area of the collection container, causing suction to be developed through the collection tubes, resulting in the breast receptors to extract milk from a mother's breast.
A disadvantage of this portable breast pump system is that the area where vacuum is to be created is relatively large, as it is also intended for receiving milk from the mother's breast. This means that the size of the container should be at least 200 milliliters. Creating a vacuum level low enough to extract milk from the mother's breast requires either strong pumping for a small amount of time or normal pumping during a longer period in time. Pumping a long period in time is not feasible, as a mother's breast is activated best for giving milk by simulating a baby sucking on the breast. Strong pumping requires a powerful motor, requiring a significant amount of energy. This conflicts with the portable character of the portable breast pump system.
Another disadvantage is that the area in which the vacuum is to be created varies in size while more milk is collected in the collection container. This means that either the suction force applied to the mother's breast varies over time or that the suction force created by the breast pump should be varied over time. The first option is disadvantageous because this affects effective milk extraction and the second option is disadvantageous as this requires additional suction control means.